A tribe of apes living in remote forests in the northern Democratic Republic of Congo are unusually large chimpanzees, not a new species of giant ape or a chimp-gorilla hybrid, New Scientist says.

Zoologists became excited after people living around Bili, a town about 200 kilometres east of the Ebola River, recounted tales of seeing huge ferocious apes with a taste for killing lions.

From photographs, the creatures were estimated to weigh about 100 kilograms and their footprints, at up to 34 centimetres, were longer than a gorilla's.

But a year-long hunt by Cleve Hicks and colleagues from the University of Amsterdam shows there is only a "negligible" chance that the enigmatic apes are a new branch of the primate tree.

Mr Hicks' team were able to observe the animals for a total of 20 hours.

"I see nothing gorilla about them. The females definitely have a chimp's sex swellings, they pant-hoot and tree-drum, and so on," he told the British science weekly, whose report appears in Saturday's issue.

Samples of a DNA recovered from faeces also put the animals in a recognised subspecies of chimp, Pan troglodytes schweinfurthii.

Even so, the Bili apes are unusual, as they have a gorilla-like crest on their skulls and howl during the full moon.

About 18 kilometres north-west of Bili, Mr Hicks came across a large community of the animals that apparently had never met a human before.

"It's fantastic. They surround us and show curiosity - even the adult males. It is these guys we want to study," he said.